Tectonic Summary

The Pulau Pagai Selatan, Sumatra earthquake of October 25, 2010 occurred as a result of thrust faulting on or near the subduction interface plate boundary between the Australia and Sunda plates. At the location of this earthquake, the Australia Plate move north-northeast with respect to the Sunda plate at a velocity of approximately 57-69 mm/yr. On the basis of the currently available fault mechanism information and earthquake depth it is likely that this earthquake occurred along the plate interface. The subduction zone adjacent to the region of this event last slipped during the Mw 8.5 and 7.9 earthquakes of September 2007, and today's event appears to have occurred near the rupture zones of those earthquakes. Today's earthquake is the latest in a sequence of large ruptures along the Sunda megathrust, including a M 9.1 earthquake that ruptured to within 800 km north of this earthquake in 2004; a M 8.6 700 km to the north between Nias and Simeulue in 2005; and a M 7.5 300 km to the north near Padang in 2009. Today's earthquake occurred near the southern edge of a Mw 8.7-8.9 rupture in 1797 and within the rupture area of a Mw 8.9-9.1 earthquake in 1833.

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